In the production of semiconductor devices, lithography capable of exposing fine patterns of 0.1 μm or less is getting into the spotlight as a promising electron beam exposure technique. This lithography has several methods, and each method has a problem to be solved. An example is a “variable rectangular beam method” which draws a pattern with one stroke. However, the throughput of this variable rectangular beam method during patterns exposure is low. Therefore, no sufficient throughput can be obtained as a mass-production exposure apparatus for efficiently drawing patterns on a large amount of wafers.
As a lithography method capable of increasing the throughput, a “pattern projection method” which transfers a pattern formed on a stencil mask by reducing the pattern is proposed. This method is advantageous to the drawing of simple patterns having a number of repetitive portions. However, the method has many problems to be solved to increase the throughput when drawing random patterns such as logic wiring layers. Therefore, the method cannot be put into practical use without interfering with the increase in productivity.
In contrast, a multi-beam system which draws patterns at the same time with a plurality of electron beams without using any mask is proposed. This system eliminates the need to manufacture a physical mask, set the mask in an exposure apparatus, and replace the mask. Accordingly, the system can be put into practical use with many advantages. For example, a multi-electron-beam exposure apparatus for drawing patterns by using a plurality of electron beams is described in “Hiroshi Yasuda: Applied Physics 63, 1135 (1994)”.
FIG. 1 is a sectional view of a blanker array used in this multi-electron-beam exposure apparatus. The blanker array is a device in which blankers having apertures and blanking electrodes are arranged in the form of an array, and can individually control emission of a plurality of electron beams. In FIG. 1, reference numerals 151 denote apertures; and 152 and 153, first and second blanking electrodes. To irradiate a sample with charged particle beams passing through the apertures, a ground potential signal is applied to the first and second blanking electrodes 152 and 153. To intercept the beams, positive- and negative-potential signals are simultaneously applied to the first and second blanking electrodes.
In the above prior art using a plurality of electron beams, it is necessary to arrange a large number of blanking electrodes in the form of an array, and independently control the blankers for turning on/off the individual beams. Therefore, if the number of blankers increases, wiring for controlling the blanking electrodes becomes difficult to form. This will be explained with reference to FIGS. 2 and 3. FIG. 2 is a plan view showing the arrangement of a 6×6 blanker array from which an interconnection to each electrode is omitted. Referring to FIG. 2, an electron beam is emitted in the direction perpendicular to the drawing surface, and passes through an aperture 151. Reference numerals 152 and 153 denote a pair of blanking electrodes used to turn on/off the electron beam. In FIG. 2, interconnections to the blanking electrodes of the individual blankers are independent of each other. FIG. 3 is an enlarged view of a portion “A” in FIG. 2, and shows a structure including interconnections to the individual blanking electrodes when these interconnections are extracted from the electrodes in the Y direction. As shown in FIG. 3, the number of interconnections increases away from the device center in the interconnection extracting direction (the Y direction in FIG. 3). This makes it difficult to connect interconnections to thousands of blanking electrodes while the blanker pitch is held constant (e.g., 100 μm).
Another problem is the contamination of a process line. To connect a number of interconnections to blanking electrodes, it is possible to form these interconnections as a multilayered wiring structure in an electrode substrate which is an MEMS substrate on which the blanking electrodes are formed. To arrange thousands of blankers at a pitch of about 100 μm, however, the unit of the wiring design rule becomes submicron, so a process apparatus for a semiconductor LSI line is necessary. Unfortunately, the semiconductor process line has the limitation on fabrication that in order to avoid heavy metal contamination, the above-mentioned MEMS substrate fabricated by the MEMS process line cannot be processed on the semiconductor process line.